Computer applications can display content from different sources as part of a single application or other single piece of content. A web page, for example, can combine images, text, and other static and interactive content from various sources. For example, a web page can be provided as a HTML page containing multiple sibling HTML nodes. Similarly, various multimedia and application players play content that includes multiple pieces from multiple sources. For example, Adobe® Flash Player®, which is built into some web browsers and available as a plugin for others, can play SWF files to present Flash® movies that includes multiple pieces from multiple sources, as well as varying degrees of interactivity, animation, and other functionality, within the web browser. Unfortunately, various problems can prevent combined content from appearing as a single piece or single application. For example, in an application, tools may not properly overlay separately specified HTML content, preventing the tools and content from having a single application feel that may be expected by users.